The invention generally relates to devices for locking a vehicle seat.
More specifically, the invention relates to a device for locking a vehicle seat of the type comprising a pawl which can be pivoted about a pivot axis and, in a closed position, is in engagement with a positionally fixed fitting and, in an open position, is free from the fitting, and a locking element for locking the pawl in the closed position.
Without limiting the general character, the locking device mentioned at the beginning can be used for anchoring a vehicle seat on the floor or for locking a pivotable backrest of a vehicle seat.
However, the preferred use of the locking device according to the present invention is the anchoring of a vehicle seat on the floor.
In the case of the locking device being used for anchoring a vehicle seat on the floor, the positionally fixed fitting with which the pawl is in engagement in its closed position is, for example, a bolt which is fixed on the vehicle body and is engaged around by a mouth of the pawl in the closed position of said mouth. The locking element serves to securely lock and, if appropriate, to clamp the pivotable pawl in its closed position. In order to transfer the pawl into its open position, an actuating element is provided which serves to transfer the locking element from its locking position into its unlocking position, after which the pawl is moved into the open position, customarily automatically by means of spring prestressing.
In particular the following two demands are imposed on locking devices of this type. Firstly, the pawl must not automatically open during the operation of the vehicle in which the vehicle seat is installed. However, in the event of an impact of the vehicle during an accident, high forces may act on the pawl and may exert a torque on the pawl in the direction of its open position. The locking element has to counteract an opening torque of this type in order to securely hold the pawl in its closed position. This can be ensured, for example, by the clamping surface of the pawl being in engagement under self-locking with the clamping surface of the locking element.
The second demand imposed on locking devices of this type is that it is easily actuable for the intended opening of the pawl. However, the previously mentioned self-locking of the engagement of the two clamping surfaces of the pawl and of the locking element counteracts such a smooth-running actuation of the locking element for opening the pawl, and therefore a construction of the locking device with self-locking bearing of the clamping surface of the locking element against the clamping surface of the pawl is only partly suitable. In addition, the self-locking depends on the surface state of the two clamping surfaces and may be reduced or even eliminated, for example by means of soiling or lubricants, such that, in the event of an impact, the remaining of the pawl in the closed position solely on the basis of an self-locking frictional connection cannot always be ensured.
In order to eliminate this problem, in the case of a locking device according to DE 44 39 644 C2, the locking element is provided, in addition to the clamping surface, with a catching surface which, upon bearing against the clamping surface of the pawl, prevents the pawl from exerting an opening torque on the locking element. For this purpose, the catching surface is designed in such a manner that it runs parallel to a displacement section between an axis of curvature of the clamping surface of the locking element and the pivot axis of the locking element. The catching surface is accordingly a planar surface with a 0° pitch with respect to the pivot axis of the locking element.
In order to ensure the smooth-running of the known locking device during intentional opening, the clamping surface of the locking element bears without self-locking against the clamping surface of the pawl in the locking position.
In a first embodiment of the known locking device, the locking element is designed as a single part, and the catching surface and the clamping surface of the locking element are arranged one behind the other in the circumferential direction about the pivot axis. In another embodiment of the known locking device, the locking element is designed as two parts, with the one part of the locking element only having the clamping surface and the other part of the locking element only having the catching surface. The two parts are coupled to each other with a movement clearance in the pivoting direction of the locking element via a pin and slot connection. The catching surface of the one part of the locking element is oriented with respect to the clamping surface of the other part of the locking element in such a manner that, in the correct closed position of the pawl, only the clamping surface of the locking element bears against the clamping surface of the pawl, and, in the event of an impact, if the clamping surface of the locking element comes out of contact with the clamping surface of the pawl, only the catching surface of the other part of the locking element bears against the clamping surface of the pawl in order to prevent further opening of the pawl.
The configuration of the known locking device with a locking element, the clamping surface of which bears against the clamping surface of the pawl without self-locking, has the disadvantage that, in order to compensate for play, so as to avoid rattling of the device during operation, a sufficiently large counterforce always has to be produced in order to keep the device, i.e. more precisely the pawl, closed, which has to be realized, for example, by means of a sufficiently high spring force.
The device which is known from the document DE 100 48 127 A1 has an actuating element, which is referred to there as a switching plate, for unlocking the pawl, with the switching plate being formed integrally with the locking element. In the event that the pawl exerts an opening torque on the locking element during an impact, the switching plate runs against a stop, as a result of which further opening of the pawl is avoided. In this case, the stop against which the switching plate runs has to absorb virtually the entire opening torque occurring during the impact because the pawl continuously exerts an opening torque on the locking element. Accordingly, the stop has to be designed for absorbing very high forces, but, due to the fact that the stop has to absorb all of the opening forces, this cannot always be ensured or ensured to an adequate degree.